There are many kinds of semiconductor sensors which have many uses. In particular, silicon sensors are widely used in imaging technologies such as video cameras, digital cameras, and optical navigation devices.
The silicon layer in the silicon CMOS image sensors used in optical navigation devices is typically made as thin as possible to minimize the amount of silicon used and obtain as compact a device as possible. Infrared light tends to pass through the silicon layer in such silicon CMOS image sensors without being absorbed. Thus, the silicon in the silicon CMOS image sensor is too thin to absorb the infrared light with a desired energy absorption efficiency.